Hi,
Sorry, that is indeed a known issue. It has been fixed already internally some time ago (see https://www.tmssoftware.com/site/forum/forum_posts.asp?TID=13546&title=autofitcol-with-wrapped-text which while for the "twin" FlexCel.NET, also applies here)
We are just 2 bugs away of releasing FlexCel 7, so it is a thing of days now. Once released, it will include the fix for this bug.